Wet Chlorine gas will create pitting corrosion due to presence of aq. but most probably Dry Chlorine gas will not harm. Others may pl. comment. regards DM

Generally Chlorine with less than 150 ppm water is regarded as dry chlorine. Regarding the material for piping, following are the few guidelines (excerpts from some HSE guidelines (www.HSE.uk.com) Chlorine The flow rate of liquid chlorine through carbon steel pipework is restricted to 2 m/s to avoid removing the ferric chloride coating on the pipe surface which protects against erosion / corrosion of the carbon steel. Wet chlorine gas corrodes mild steel. PVDF (preferably), ebonite, or rubber lined steel is used for this duty. Chlorine gas handled at temperatures in excess of 200°C in carbon steel can result in chlorine / steel fires. Zinc can be used for this duty, but for low temperature (e.g. liquid) chlorine special steels are required to avoid embrittlement. Titanium is unsuitable for Chlorine duty and should be avoided. However, Titanium manufacturers advise the use of Ti Gr. 2 piping (ASTM B 861 or 862) for wet chlorine. 'Seems govt agencies do have some inhibition regarding use of Ti piping. Basically, CS is passivated by dry Chlorine ( a layer of FeCl3) whereas Titanium is passivated by wet Chlorine (mnim 1-2% water). Ti may suffer crevice corrosion. Stainless steels are unsuitable for Chloride service. 'Hope it helps. Regards